If you get this error when running NAMD:

libstdc++.so.5: cannot open shared object file: No such file or directory

Then you need to install the compat-libstdc++-33 package (on Red Hat):

yum install compat-libstdc++-33

or, if you have the RPM:

rpm -i compat-libstdc++-33-3.2.3-47.3.i386.rpm

-JimPhillips